Tim Allen may have brought joy to millions over the course of the beloved holiday film franchise, The Santa Clause, but as it turns out, stepping into the iconic holly, jolly costume brought the actor little joy in return.

The actor is one of many who sat down with A Christmas Story star Peter Billingsley for a new 20/20 Christmas special, entitled "Lights, Camera, Christmas: Inside Holiday Movie Classics," to take viewers behind the scenes of their holiday favorites, dissecting the most memorable moments from some of the films. And in this preview of Allen's interview, exclusive to E! News, he doesn't hold back on the downside to bringing Santa to life.

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"You are Santa Claus, with the beard and the hair and, of course, all the additional pounds in the fat suit," Billingsley says. "Did you have any idea what you were signing up for?"

"Innocence is bliss," Allen admits, going on to say that there's no way to get around how uncomfortable the three hours of preparation it took to transform him into the iconic character really were.

"I overhear, 'He can't be in that more than six hours' because your skin doesn't breathe and you get these sores all over you," he reveals. "They go, 'Well, they'll go away.' I hear them arguing in a room. They'll go away?!" Yikes!

The special will also include interviews with Allen's The Santa Clause co-star Eric Lloyd, National Lampoon's Christmas Vacation's Chevy Chase and Beverly D'Angelo, Mel Gibson (representing recently-released Daddy's Home 2) and Brian Grazer, who produced the Jim Carrey-starring How the Grinch Stole Christmas.

The special will also consider the age-old question of whether favorites like Die Hard and Trading Places qualify as Christmas movies, talk to a spokesperson from Rotten Tomatoes about what it takes to qualify as a Christmas classic, and look at the the history of small-screen favorites like A Charlie Brown Christmas and Rudolph the Red-nosed Reindeer, including interviews with the voice-over artists behind those animated characters.